"He came to this location yesterday afternoon – late – and came under the guise of a FedEx driver wearing a FedEx shirt," said Constable Ron Hickman. "…came to this residence, gathered up the children that were here and awaited the arrival of the parents. Sometime later the victims were shot in this residence, and we now learned that Mr. Haskell was married to a relative of the residents of this home."

Haskell's estranged wife lives out of state and was not at the home.

Authorities described the dead as two boys, ages 4 and 14; two girls, ages 7 and 9; a 39-year-old man; and a 33-year-old woman.

In court early Thursday, prosecutors said Haskell tied up the family, placed them face down, and then shot each of them in the head execution style.

Deputies said a 15-year-old survivor of the mass shooting suffered a bullet fracture to her skull. She played dead until the suspect left and then alerted authorities that the gunman was on his way to her grandparents' home to kill more relatives.

The deputies beat him to that home and a standoff ensued. After more than three hours sitting in a cul-de-sac, Haskell surrendered.

During that time, Deputy Thomas Gilliland of the Harris County Sheriff's Office said, there were "two hours of constant talking with a man armed with a pistol to his head and who had just killed six people."

Gilliland described the man as in his 30s with a beard "and cool as a cucumber." He said that when he and other officers first approached, the man was "just sitting in his car looking out at us."

"This concluded the way we wanted it to," Gilliland said after the surrender.

Gilliland said the teenager who survived was in "very critical condition" at Memorial Hermann Hospital in Houston as of late Wednesday night.

Authorities have not yet released the names of the victims who were killed.

Contrary to earlier statements made by authorities, Haskell's adopted kids were not among the shooting victims.

As he was transferred to the county jail, the suspect was still wearing the FedEx uniform, but authorities said it's not yet clear if he was actually employed by the shipping company.